Electronic-parts mounting board and electronic-parts mounting board frame

ABSTRACT

An electronic-parts mounting board frame is formed by assembling a plurality of electronic-parts mounting boards into a single frame. The mounting boards may be electrically connected to the frame by separate inner and outer lead frames, the former being formed in the mounting boards and the latter being integral with the frame.

This application is a Division of application Ser. No. 07/797,032, filedNov. 25, 1991, now U.S. Pat. No. 5,274,197.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic-parts mounting board, andan electronic-parts mounting board frame with a plurality ofelectronic-parts mounting boards assembled thereinto.

2. Discussion of the Related Art

Various types of electronic-parts mounting boards have been proposed.One of those known electronic-parts mounting boards is anelectronic-parts package, or a semiconductor device. In the package,after an electronic part is mounted on the board, the board is entirelycovered for sealing purposes with a so-called resin mold, while theouter leads of the board protrude outwardly from the resin mold.

An electronic-parts mounting board sealed with a resin mold is disclosedin Japanese Patent Laid-Open Publication No. Sho. 59-98545, entitled"Pellet Mounting Board," which is for a semiconductor device. Thepublication claims a pellet mounting board "wherein a pellet is mountedon a pellet mounting board with a conductive layer, bonding pads of saidpellet are electrically connected to said conductive layer by a wirebonding method, and said conductive layer of said pellet conductivelayer by a wire bonding method, and said conductive layer of said pelletmounting board is bonded to a lead frame." The disclosed pellet mountingboard suffers from the following problems, however:

1) Solder is used for bonding the conductive layer of the pelletmounting board (referred to as a board) to the lead frame. Each portion(pad) subjected to the soldering lies on an insulating substrate.Accordingly, the pad tends to peel off the insulating board when it isheated for soldering.

2) The insulating substrate is located between the pads. Soldermistakenly left on the insulating substrate possibly may cause anelectrical short between the pads.

3) The thermal expansion coefficient of the board is different from thatof the lead frame. When the pellet (electronic part) heats, the leadframe tends to peel off the board. One possible cause of the peel-off iswarping of the lead frame.

4) The major surfaces of the insulating substrate do not fully utilizethe space available to form the conductive circuits.

To cope with the above problems, an electronic-parts mounting board hasbeen proposed which is constructed such that an insulating substrate isapplied to both sides of the lead frame, to form a one piececonstruction, and the conductive circuits on the insulating substrateare electrically connected to the leads through the through-holes.

To be more specific, the proposed mounting board uses lead frames eachhaving leads, connected by tie bars, that are constructed such thatinner leads are electrically connected to the conductive circuitsthrough the through-holes, and outer leads protrude from both theinsulating board and the resin mold and are physically continuous.

The electronic-parts mounting board thus constructed still involvesunsolved problems, however, as follows:

5) In recent usage of the electronic-parts mounting board, a pluralityof electronic-parts mounting boards are assembled into a frame, in orderto routinely and efficiently mount electronic parts on the board and toseal the structure with a resin mold. To assemble the insulating boardbased electronic-parts mounting boards into the lead frame, a singlemetal plate is punched to form leads in the locations where a pluralityof electronic-parts mounting boards are to be formed. Insulatingsubstrates, separately formed, are coupled with the leads.

6) In the electronic-parts mounting boards thus assembled into oneframe, if a part of the lead frame is defective, the whole lead framemust be treated as being defective. Accordingly, the remainingnon-defective parts of the lead frame are wasted. The portions of thelead frame to be used for the electronic-parts mounting boards requireespecially delicate working for their formation. The cost to form thoseportions is higher than that to form other portions. Therefore,replacement of only those portions to be used for the electronic-partsmounting boards with non-defective portions would be very advantageous.

7) Since a plurality of electronic-parts mounting boards are assembledinto a single lead frame, the whole lead frame must be individuallydesigned and manufactured so as to have a shape in conformity with theshape of the electronic-parts mounting boards. In this respect, theversatility of the lead frame in usage is poor.

8) The electronic-parts mounting board must be subjected to electricalchecks or tests in the stages of manufacturing the board. Certainty ofthe process of subjecting the board to electrical testing would behighly advantageous.

Studies made by the inventors to solve the above problems and to reducethe disadvantages of the electronic-parts mounting board have resultedin the present invention.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstancesand has as an object the provision of an electronic-parts mounting boardand an electronic-parts mounting board frame in which, when a part ofthe board and the board frame is defective, only the defective part canbe replaced with a non-defective one, thereby providing a highproduction yield, high reliability, and low cost.

Another object of the invention is to provide an electronic-partsmounting board and an electronic-parts mounting board frame in whichsimplified electrical testing may be accomplished during manufacture.

An additional object of the invention is to provide an electronic-partsmounting board and an electronic-parts mounting board frame in whichonly a defective part can be replaced and in which handling and framingof the boards is simplified.

Finally, yet another object of the invention is to provide anelectronic-parts mounting board having a standardized inner lead frameand a mounting board frame with integral but separate, and thereforeeasily customized, outer lead frames for electrical connection with thestandardized inner lead frame.

To achieve the above objects, the invention preferably provides anelectronic-parts mounting board frame constructed such that a pluralityof electronic-parts mounting boards are assembled into a single frame,wherein a plurality of leads formed in each electronic-parts mountingboard are formed from a member discrete from the member constituting theframe, and are electrically connected to the frame.

In the preferred electronic-parts mounting board frame, a plurality ofelectronic-parts mounting boards are separately formed. Those boards areassembled into a frame by means of leads. Therefore, a defectiveelectronic-parts mounting board, may be replaced with a non-defectiveboard without wasting other non-defective boards.

According to another aspect of the invention, there is provided anelectronic-parts mounting board frame constructed such that a pluralityof electronic-parts mounting boards are assembled into a single frame,wherein a plurality of leads for each electronic-parts mounting boardinclude outer leads integral with the frame and inner leads formed of adiscrete member separate from the frame and the outer leads, aninsulating substrate is applied to both sides of the inner leads suchthat the inner leads protrude from the insulating substrate and theprotruding inner leads are electrically connected to the outer leads,whereby the plurality of electronic-parts mounting boards are assembledinto the frame.

Thus, in this preferred electronic-parts mounting board frame, the leadsinclude the inner leads to which the insulating substrate is applied,and the separate outer leads to be connected to the inner leadsprotruding from the insulating substrate. More specifically, theinvention preferably includes an inner lead frame in which the innerleads are connected by tie bars, and an outer lead frame including outerleads which are integral with the frame, the inner and outer lead framesbeing electrically connected by, for example, soldering.

According to still another aspect of the invention, there is provided anelectronic-parts mounting board frame constructed such that a pluralityof electronic-parts mounting boards are assembled into a single mountingboard frame, wherein a plurality of electronic-parts mounting boards areassembled into the mounting board frame, to form a one-piececonstruction in such a manner that an insulating substrate is applied toboth sides of the lead frames, each lead frame including an individuallyformed outer frame which is fixed to the mounting board frame.

In this variation of the inventive electronic-parts mounting boardframe, the outer frame is provided on the peripheral side of the leadsto which the insulating substrate is applied. When the plurality of theelectronic-parts mounting boards are assembled into one mounting boardframe, the outer frame of each electronic-parts mounting board is fixedto the mounting board.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification illustrate embodiments of the invention and,together with the description, serve to explain the objects, advantagesand principles of the invention. In the drawings,

FIG. 2 is a plan view showing in enlarged fashion how eachelectronic-parts mounting board is coupled with a frame;

FIG. 3 is a plan view showing an electronic-parts mounting board frameaccording to a second embodiment of the invention, the illustrationtypically showing one electronic-parts mounting board in connection witha frame;

FIG. 4 is a plan view showing an inner lead frame of theelectronic-parts mounting board used in the electronic-parts mountingboard frames of FIG. 3;

FIG. 5 is a plan view showing the inner lead frame when an insulatingsubstrate is applied to the lead frame, and tie bars are removed fromthe lead frame;

FIG. 6 is a plan view showing one of outer lead frames 13 with which theelectronic-parts mounting board shown in FIG. 5 is to be coupled;

FIG. 7 is a diagram showing one of the coupling modes when the innerlead portions of the electronic-parts mounting board are connected tothe outer lead portions of the outer lead frame, the illustrationtypically showing the connection of one inner lead portion to one outerlead portion, for simplicity;

FIGS. 8 and 9 are diagrams showing additional coupling modes;

FIG. 10 is a vertical sectional view showing in enlarged fashion asemiconductor device using the electronic-parts mounting board of theelectronic-parts mounting board frame according to the secondembodiment;

FIG. 11 is a partial enlarged plan view showing an electronic-partsmounting board frame according to a third embodiment of the invention;

FIG. 12 is a sectional view taken on line XII--XII in FIG. 11;

FIG. 13 is a partial enlarged plan view showing a modification of theelectronic-parts mounting board frame according to the third embodiment;

FIG. 14 is a sectional view taken on line XIV--XIV in FIG. 13;

FIG. 15 is a sectional view showing another connection of the frame 30to the leads 11 according to the first embodiment of the invention;

FIG. 16 is a partial enlarged plan view showing an additionalmodification of the connection of the frame and the outer lead frame inthe third embodiment;

FIG. 17 is a vertical sectional view showing a semiconductor deviceconstructed using the electronic-parts mounting board of FIG. 11;

FIG. 18 is a sectional view showing a further connection of the innerand outer lead portions 11a and 11b according to the second embodimentof the invention; and

FIG. 19 is a sectional view showing another connection of the frame 20and the outer frame 31 according to the third embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate an electronic-parts mounting board frame 100according to a first embodiment of the present invention. As showntherein, four electronic-parts mounting boards 10 are mounted on asingle frame 20, to form a single unit. In each electronic-partsmounting board 10, an insulating substrate 14 is applied to the innersides of groups of leads 11, and the inner sides of the boards and theleads groups are unified into a single piece construction. As shown inFIG. 10, conductive circuits 15 formed on the insulating substrate 14are selectively and electrically connected to the grouped leads 11through through-holes 16. The external ends of the respective leads 11,as shown in FIG. 2, protrude from the insulating substrate 14. Theelectronic-parts mounting board 10, which is to be assembled into theelectronic-parts mounting board frame 100, may be completed as asemiconductor device 200, after an electronic part 40 is mountedthereon. In this case, as shown also in FIG. 17, the end faces of a moldresin 50 thereof are positioned on the leads 11. Thus, the frame 20 isused only for supporting each electronic-parts mounting board 10 bymeans of the leads 11. In the semiconductor device 200 as shown in FIGS.10 and 17, the frame is not used.

The frame 20, as shown in FIG. 1, is a plate-like member with a numberof openings 5 for receiving the electronic-parts mounting boards 10.With the shape of the frame as illustrated, the frame 20 has a rigidityhigh enough not only to support the electronic-parts mounting boards 10but also to allow the frame itself to be transferred to a mountingapparatus for mounting the electronic parts 40 and a transfer moldapparatus for the mold resin 50.

The electronic-parts mounting boards 10 are mounted on the frame 20 insuch a manner that the leads 11, as shown in FIG. 2, are connected attheir tips to the frame 20 by suitable means, such a spot welding orsoldering, for example. In this instance, to connect the leads 11 to theframe 20, the leads 11 are directly placed on the frame 20, as shown inFIG. 2. Alternatively, the tips or ends of the leads may abut againstthe frame as shown in FIG. 14 or the half-etched ends of the leads maybe coupled with the half-etched edge of the frame as shown in FIG. 15.

In the electronic-parts mounting board frame 100 thus constructed, whichis the first embodiment of the invention, a plurality ofelectronic-parts mounting boards 10 are assembled into one frame 20 andfixed thereto by means of the grouped leads 11. With this construction,if one of the electronic-parts mounting boards 10 is defective, thedefective board may be replaced with a non-defective one, while theremaining ones may be used as they are. The electronic-parts mountingboard frame 100 is of course constructed so as to provide for efficientmounting of the electronic part 40 and to seal the substantially wholeelectronic part 40 within the mold resin 50, as shown in FIG. 10 or 17.

The electronic-parts mounting board frame 100 includes two separatemembers; one member is for the leads 11 for the electronic-partsmounting boards 10, and the other is for the frame 20 for supporting theelectronic-parts mounting boards 10. As a result, the cost ofmanufacture of the electronic-parts mounting board frames 100 is reducedbecause the simpler structure members, i.e., the frames 20, and the morecomplicated members, such as leads 11, may be separately manufactured.Furthermore, the cost to manufacture the semiconductor devices 200 usingthe electronic-parts mounting boards 10 is also reduced. When the boardsare used for the semiconductor devices 200, the frames 20 are not used.Those frames may be used later, if required.

The electronic-parts mounting boards 10 are individually manufactured asproducts having the leads 11. Therefore, those boards can beelectrically tested board by board. The leads when electricallyseparated as shown in FIG. 2, may also be tested in a simple manner leadby lead.

A second embodiment of an electronic-parts mounting board frame 100according to the present invention will be described with reference toFIGS. 3 to 10 and 18. In this embodiment of the frame 100, the leads 11for connecting the electronic-parts mounting board 10 to externalcomponents or devices are each divided into two portions, an inner lead11a and an outer lead 11b. The jointed portions of the inner and outerleads 11a and 11b are disposed within the mold resin 50, when theelectronic-parts mounting boards 10 are completed as the semiconductordevices 200, as shown in FIG. 10. In the figures, a singleelectronic-parts mounting board 10 and its related parts are illustratedfor simplicity. The frame 20 is located outside an outer lead frame 13integral with groups of outer leads 11b. A plurality of outer leadframes 13 are assembled into a single frame 20, to form a single unit.

FIG. 3 is a plan view showing one of the electronic-parts mountingboards 10, which are to be assembled into an electronic-parts mountingboard frame 100 according to the present invention. An insulatingsubstrate 14 including conductive circuits 15 is disposed in the centralpart of the board. The outer leads 11b of the leads 11 protrude from theinsulating substrate 14. The leads 11 of the board 10 are constructedsuch that the inner leads 11a of an inner lead frame 12 are electricallyand physically connected to the outer leads 11b of the outer lead frame13, respectively, by suitable means, such as by soldering.

For forming the electronic-parts mounting boards 10, a plurality ofinner lead frames 12 as shown in FIG. 4 and a plurality of outer leadframes 13 as shown in FIG. 6 which are assembled into the frame 20 areprepared. The inner lead frames 12 and the outer lead frames 13 whichare assembled into the frame 20 are separately manufactured. The frame12 shown in FIG. 4 is formed by punching or etching out of a metal plateinner leads 11a, which are connected by means of tie bars 12a. The metalplate is made of a material such as 42 alloy or copper compositematerial. An insulating substrate 14 on which conductive circuits 15have been formed or are to be formed, is applied to the central part toform a unit, as shown in FIG. 5, in which the inner leads 11a are causedto protrude from the insulating substrate 14. The protrusion of theinner leads 11a is made because the inner leads 11a must be coupled withthe outer leads 11b in later manufacturing steps. In the inner leadframe 12 shown in FIG. 4, a terminal 11c which will serve as a baseterminal or ground terminal is formed in the central part toward whichthe inner leads 11a are extended. Preferably, some of the inner leads11a are connected to a central terminal 11c. The central terminal 11cis, however, not essential to the invention.

As shown in FIG. 10, necessary conductive circuits 15 are formed on theinner lead frame 12 with the insulating substrate 14 applied thereto asshown in FIG. 5, and through-holes 16 are formed therein to electricallyconnect the conductive circuits 15 to the inner leads 11a. In the innerlead frame 12, both sides of which are covered with the insulatingsubstrate 14, the tie bars 12a which tie the inner leads 11a togetherare cut off, for example, by a press machine, as shown in FIG. 5. As aresult, although the inner leads 11a are each electrically connected tothe conductive circuits 15 on the insulating substrate 14 through thethrough-holes 16, they nevertheless protrude separately from theinsulating substrate 14.

Let us consider the outer lead frames 13 which are assembled into theframe 20. Typically, in one outer lead frame 13, as shown in FIG. 6, theouter leads 11b are connected by tie bars 13a, the lead frame beingpunched out of a metal plate made of 42 alloy or copper compositematerial, for example. In the illustrated example, the number of innerleads 11a of the inner lead frame 12 is equal to the number of outerleads 11b of the outer lead frame 13. However, if required, the numbersof leads need be not equal to each other. For example, where theelectronic-parts mounting board is used as a semiconductor device 200,the number of outer leads 11b of the outer lead frame 13 need only bethat required for the semiconductor device 200.

In assembling the electronic-parts mounting board frame, the outer leadframes 13 thus constructed are positioned so that the ends of the outerleads 11b respectively confront the ends of the inner leads 11a of theinner lead frame 12. Then, those leads are electrically connected bysoldering, for example, and the tie bars, 13a, which are nowunnecessary, are cut off for removal by well known means. Finally, theelectronic-parts mounting boards 10 are formed. In this case, the innerleads 11a and the outer leads 11b may be connected by using

a) solder as just mentioned,

b) conductive adhesive,

c) anisotropic conductive rubber, or

d) any other suitable connection means.

If any of those is used, the connecting work is performed while securingthe electrical conduction therebetween.

In connecting leads 11a and 11b, the lead shapes may be varied,providing beneficial effects. For example, the outer leads 11b may berelatively wide as shown in FIG. 7, to increase their rigidity. Theleads 11a and/or 11b may also be shaped so as to have enlarged tips, asshown in FIG. 8. The enlarged tips are suitable for more securelyholding solder or adhesive. Additionally, the tips of the leads may beapertured as shown in FIG. 9. With the apertured tips, solder oradhesive is even more securely held, increasing adhesive strength.Further, as shown in FIG. 18, the tips of the leads 11a and 11b may behalf-etched to form stepped parts. The stepped parts of the leads arelaid one upon the other for coupling purposes as shown in FIG. 18. Inthis case, the jointed portion of the leads thus coupled have smoothedsurfaces.

As already stated, in manufacturing a plurality of inner lead frames 12and a plurality of outer lead frames 13 assembled into the frame 20,both frames making up the electronic-parts mounting board frame 100, ametal plate is formed into predetermined patterns by a suitable means,such as by punching. For example, a single metal plate may be punched toform the inner lead frames 12 or the outer lead frames 13. That is, anumber of lead frames may be punched out of a single metal plate. Inthis case, the punching work is applied separately to the inner leadframes 12 or the outer lead frames 13. This simplifies theirmanufacture, and improves the efficiency of the manufacturing operation.In the instant embodiment, 150 inner lead frames 12 were punched out ofa 1/6 square meter copper plate. 42 outer lead frames 13 correspondingto the inner lead frames 12 were punched out of a 1/8 square meter42-alloy plate.

The electronic-parts mounting board frame 100 thus constructed ismanufactured in the following manner: The insulating substrate 14 ispressed on both sides of each inner lead frame 12, so that those arecombined into a single unit. Necessary conductive circuits 15 andthrough-holes 16 are formed on and in the structure. Thereafter, the tiebars 12a are cut off to form the inner leads 11a, which are caused toindependently protrude from the insulating substrate 14. Then, theelectrical connection of the inner leads 11a to the conductive circuits15 through the through-holes 16 is checked for each of theelectronic-parts mounting boards 10, and the electronic-parts mountingboards having defective electrical connections are removed. Thenon-defective electronic-parts mounting boards 10 are thus selected and,as shown in FIG. 3, assembled into the outer lead frames 13 which havebeen assembled into the frame 20.

An electronic part (e.g., a semiconductor element) 40, as shown in FIG.10, is mounted on one or both sides of the insulating board 14 of eachelectronic-parts mounting board 10. The electronic part 40 and theconductive circuit 15 are electrically connected by a bonding wire 41.Finally, the structure is entirely sealed with mold resin 50 thuscompleting, in this example, an intended semiconductor device 200.

The electronic-parts mounting boards 10 making up the electronic-partsmounting board frame 100, in the second embodiment of the invention, maybe used for forming the semiconductor device 200, as shown in FIG. 10.To form the device, the electronic part 40 is mounted on theelectronic-parts mounting board 10. The structure is entirely sealedwith the mold resin 50, in a state in which the outer leads 11b extendoutwardly. The electronic-parts mounting boards 10 thus formed areassembled into the frame 20 by using the leads 11. An additionalembodiment to be described later employs an assembly in which aplurality of outer leads 11b of each electronic-parts mounting board 10are assembled into a single frame 20, and in which the electronic-partsmounting boards 10 are assembled into the frame 20 and fixed thereto bythe leads 11.

In the electronic-parts mounting board frame 100, the leads 11, as alsoshown in FIG. 3, are formed by connecting the inner leads 11a and theouter leads 11b by means of solder, for example. As already stated, theleads 11a and 11b are formed of different members. The outer leads 11bare protected by the frame 20. Those leads 11a and 11b wheninterconnected are electrically continuous and are shaped to correspondto that of frame 20. Specifically, the electronic-parts mounting boardframe 100 is formed in such a way that the insulating substrate 14 isapplied to both sides of the inner lead frames 12 as shown in FIG. 4,thereby combining them into single units, and the single units areassembled into outer lead frames 13, and the outer lead frames 13 areenclosed by the frame 20 as shown in FIG. 6.

In the structure shown in FIG. 5, after the tie bars 12a are cut off,electrical tests are performed on the inner leads 11a and the conductivecircuits 15 coupled therewith, independently of the outer leads 11b. Theresult is that only non-defective inner lead frames 12 are used for theresultant electronic-parts mounting board frame 100. Therefore, theproduct quality, particularly the electrical performances, of the framesis improved in comparison with products in which the leads arecontinuous.

This fact also improves production yield in manufacturing theelectronic-parts mounting board frames 100. The inner leads 11a and theouter leads 11b coupled with the frame 20, which cooperate to form theleads 11 and tend to be defective, may be electrically testedindividually, before the electronic-parts mounting boards 10 containingthem are assembled. Therefore, the electronic-parts mounting boards 10assembled from those electrically tested leads 11a and 11b have muchfewer defects, providing an excellent production yield.

In accordance with the invention, the inner lead frames 12 and the outerlead frames 13 coupled to the frame 20 are formed of different discretemembers. Further, in forming the lead frames, increased tolerances forthe inner and outer leads 11a and 11b are possible. The number of leadframes that can be punched out of a metal plate of a fixed area is aboutthree times the number of lead frames in which the leads consist ofphysically continuous inner and outer leads. For example, the presentinvention has been made to achieve a yield of about 900 pieces/squaremeter, while in the case of continuous leads the yield achieved was 336pieces/square meter.

The inner lead frames 12, each having a preset number of inner leads11a, are manufactured as standard products. In this case, the presentnumber of the leads 11a is preferably as large as possible. The outerlead frames 13 having the outer leads 11b protected by the frame 20 maythen be separately customized for different types of products. In thisway, the electronic-parts mounting board frame 100 itself can be readilystandardized while nevertheless permitting use in a variety of differentapplications. This is a very beneficial feature in view of recent markettrends calling for customized manufacture of small numbers of productsfor each of a variety of different applications.

In the semiconductor device 200 based on the electronic-parts mountingboard frames 100, the outer leads 11b not only extend outside the device200 but furthermore are designed to be directly connected to otherboards. Therefore, the outer leads 11b must be sufficiently rigid tosatisfy such usages. In the electronic-parts mounting board frame 100,different members are used for the inner lead frames 12 of the innerleads 11a and the outer lead frames 13 of the outer leads 11b.Therefore, the member selected for the outer lead frames 13 may have ahigher rigidity than the member for the inner lead frames 12. Theelectronic-parts mounting board frames 100 may be designed so that theirouter leads 11b have satisfactorily high rigidity.

A third embodiment of an electronic-parts mounting board frame 100according to the present invention will be described with reference toFIGS. 11 to 14, 16, 17, and 19. In this embodiment, the electronic-partsmounting boards 10 are assembled into the frame 20 by using a lead frame30. The lead frame 30 is formed by unifying groups of leads 11 by meansof an outer frame 31. To be more specific, to form the lead frame 30,grouped leads 11 for the electronic-parts mounting board 10 areconnected by means of tie bars and the external ends of the leads 11 areconnected to the outer frame 31. An insulating substrate 14 is appliedto both sides of the central part of the lead frame 30. Then, necessaryconductive circuits 15 are formed on the structure, and through-holes 16are formed in the structure. The electronic-parts mounting boards 10thus constructed, as shown in FIGS. 11 and 12, are each fixed to oneframe 20 at the peripheral edge 31 of the lead frame 30.

As described above, in the embodiment shown in FIGS. 11 and 12, theelectronic-parts mounting boards 10 are assembled into the frame 20 byutilizing the outer frame 31 located at the tips of the leads 11. To fixthe frame 31 into the frame 20, both sides of the outer frame 31 areplaced on the frame 20, and spot welded at the black points shown inFIG. 11 by resistance welding.

In this case, the inner side of the frame 20 and both sides of the outerframe 31 may be half-etched in order to form steps, as shown in FIG. 19.When the frames 20 and 31 are coupled, the stepped parts are laid oneupon the other. The jointed portions of the frame 20 and the outer frame31 have smoothed surfaces. With the smoothed surfaces of the jointedportions, the electronic-parts mounting board frame 100 may be easilypositioned in or out of related equipment as necessary. In thisembodiment, the frame 20 and the lead frame 30 are both made of copperalloy.

A modification of the coupling of the electronic-parts mounting boards10 with the frame 20 is illustrated in FIGS. 13 and 14. In thismodification, as shown, both sides of the outer frame 31 have portions32 protruding therefrom. The inner sides of the frame 20 have indentedportions 21 shaped with a U-shape. When coupling the inner and outerframes, the protruding portions 32 of the frame 31 are inserted into theU-shaped indented portions 21 of the frame 20, respectively, and arefixed by or seam welding with electron beams. The electronic-partsmounting board 10 is automatically positioned with respect to the frame20 when the protruding portions 32 are inserted into the indentedportions 21. As a result, no stepped portions in the surface of theframe 20 are required. This provides a smooth positioning of theelectronic-parts mounting board frames 100.

The embodiment of FIG. 13 may be further modified as shown in FIG. 19.In this modification, the faces of the protruding portions 32 which areto be jointed, and the indented portions 21, are half-etched to bestepped as shown. For coupling the board with the frame, the steppedportions are laid one upon the other. As in the previous modification,no stepped portions are formed in the jointed portion of the protrudingportions 32 and the indented portions 21, providing for smooth framepositioning. The frame 20 and the lead frame 30 are both made of 42alloy.

A modification of the third embodiment of an electronic-parts mountingboard frame 100 according to the present invention will be describedwith reference to FIG. 16. In this modification, the lead frame 30 andthe frame 20 include, respectively a protruding portion 32 and anindented portion 21, as in the embodiment of FIG. 13. The protrudingportion 32, which protrudes from a location at the midpoint of the sideedge of the lead frame 30, is larger than the indented portion 21. Theprotruding portion 32 has a pilot hole 32a at the center. The pilot hole32a is used when the electronic-parts mounting board frame 100 istransferred and the frame per se is applied to a related equipment. Theprotruding portion 32, when located at the midpoint of the side edge ofthe lead frame 30, reliably positions the electronic-parts mountingboard 10 when work is applied to the board. The fact that the protrudingportion 32 is larger than the indented portion 21, results in easyrepositioning of the electronic-parts mounting board 10 in the frame 20.Spot welding by a YAG laser is applied to the overlapping portion of theprotruding portions 32 within the frame 20, to couple them. In thisembodiment, the frame 20 is made of copper alloy, and the lead frame 30is made of 42 alloy.

As described above, in the electronic-parts mounting board frame 100according to the third embodiment shown in FIGS. 11 to 14, 16 and 19,the grouped leads 11 for each electronic-parts mounting board 10 arecoupled together by the outer frame 31, to form the lead frame 30. Theouter frame 31 of the lead frame 30 of each electronic-parts mountingboard 10 is assembled into the frame 20, to thereby form anelectronic-parts mounting board frame 100. If one or more of the leadframes 30 of the electronic-parts mounting boards 10 assembled into theelectronic-parts mounting board frame 100 is defective, the board 10containing the defective lead frame 30 may be removed or replaced by anon-defective one. The remaining boards can be used as they are.

The conventional lead frame consists of a plurality of parts in order toform a number of electronic-parts mounting boards 10. On the other hand,in the present invention, the lead frames 30 for the electronic-partsmounting boards 10 are individually formed. In manufacturing, theelectronic-parts mounting board 10 experiences many manufacturing steps.For example, an electronic part 40 is mounted on the electronic-partsmounting board 10. To ease the manufacturing work, the outer frames 31of the lead frames 30 of the electronic-parts mounting boards 10 areassembled into a single frame 20, as shown in FIG. 1

As described above, the present invention brings about many beneficialfeatures.

In the electronic-parts mounting board frame 100 according to the firstembodiment, a plurality of electronic-parts mounting boards 10 areassembled into one frame 20 and fixed to the frame by grouped leads 11,to thereby form a single piece construction. If any of theelectronic-parts mounting boards 10 is defective, only the defective oneis removed and replaced with a non-defective one, while the remainingnon-defective boards are used as they are. Therefore, the cost tomanufacture the electronic-parts mounting board 100 is reduced.Electrical testing of the electronic-parts mounting boards 10 can beaccomplished before the electronic-parts mounting boards 10 areassembled into the frame 20. Therefore, the fixing work of the boards tothe frame is efficiently done, and the production yield of theelectronic-parts mounting board frames 100 is improved.

By assembling the electronic-parts mounting boards 10 into the frame 20,the electronic parts 40 may be efficiently mounted on theelectronic-parts mounting boards 10. Particularly if the frames 20 eachhaving a prescribed pattern are previously manufactured, theelectronic-parts mounting boards 10 may be routinely assembled using anautomated mounting equipment for mounting the electronic parts 40.Therefore, the electronic-parts mounting board frame 100 is especiallyconvenient when semiconductor devices 200 are formed by theelectronic-parts mounting boards 10.

In the electronic-parts mounting board frame 100 according to the secondembodiment, the leads 11 for each electronic-parts mounting board 10include inner leads 11a and outer leads 11b. The inner leads 11a towhich the insulating substrates 14 are applied, and the outer leads 11bintegral with the frame 20, are formed of different members.Accordingly, the electronic-parts mounting board frame 100 of thisembodiment enjoys the same advantages as does the first embodiment. Inparticular, the inner lead frames 12, which are difficult to manufactureand expensive, may be used for each electronic-parts mounting board 10.This allows only the non-defective electronic-parts mounting boards 10to be used for the electronic-parts mounting board frame 100. The resultis to reduce the cost and improve manufacturing yield of the resultantelectronic-parts mounting board frames 100.

Additionally, a number of the inner leads 11a and a number of the outerleads 11b, which make up the leads 11, may be previously manufactured.The conductive circuits 15 on the insulating substrate 14, areselectively connected to the inner leads 11a, through the through-holes16. The electronic-parts mounting boards 10 thus manufactured have anexcellent versatility in usage.

In the electronic-parts mounting board frame 100 according to the thirdembodiment, the lead frames 30 are previously manufactured for theelectronic-parts mounting boards 10. The lead frames 30 are assembledinto and fixed to the frame 20 by the outer frames 31, to thereby form asingle piece construction. Therefore, the third embodiment hasadvantages comparable with those obtained by the first embodiment.

Furthermore, in this embodiment, a number of leads 11 necessary for theelectronic-parts mounting board 10 are unified by each outer frame 31,to thereby form lead frames 30. The lead frames 30 thus formed areassembled into and fixed to the frame 20 by the outer frames.Accordingly, the lead frames 30 may be formed individually, leading tocost reduction.

The lead frames 30 may be connected to the frame 20 in such a mannerthat protruding portions 32 of the lead frames 30 are inserted intoindented portions 21 of the frame 20. In this case, the resultantelectronic-parts mounting board frame 100 is entirely flat in shape. Thepositioning of the electronic-parts mounting boards 10 to the frame 20is therefore simplified.

As seen from the foregoing description, the electronic-parts mountingboards 10 to be assembled into one frame 20 may be manufactured indifferent forms. This feature is very useful for customized manufactureof small volumes of different products. When the electronic-partsmounting boards 10 are connected to the frame 20 by laying thehalf-etched portions one upon the other, the resultant electronic-partsmounting board frame 100 is planar in shape. The planar shape provides,for example, for smooth positioning, of the electronic-parts mountingboard frame 100 on a mounting equipment for mounting electronic parts40.

Finally, it will be understood by those skilled in the art that thephrase electronic-parts mounting board refers to a board on which eithera plurality of electronic parts or a single electronic part is mounted.The principles of the invention apply equally to either situation and itis consequently intended that the phrase electronic parts mounting boardas used in the above description and the appended claims be construed tomean any board on which at least one electronic part could be mounted.

What is claimed is:
 1. An electronic-parts mounting board framecomprising:a plurality of electronic-parts mounting boards respectivelyprovided with insulating substrates; a single frame into which saidplurality of electronic-parts mounting boards are assembled; a pluralityof outer leads formed integrally with said frame; and a plurality ofinner leads fixed at first ends to said insulating substrates of saidelectronic-parts mounting boards; wherein second ends of said pluralityof inner leads are electrically connected to ends of said plurality ofouter leads, whereby said plurality of electronic-parts mounting boardsand said frame form a single unit.
 2. An electronic-parts mounting boardframe according to claim 1, in which each said outer lead is wider thaneach said inner lead.
 3. An electronic-parts mounting board frameaccording to claim 1, in which one of the group consisting of the endsof said outer leads or the second ends of said inner leads are expandedin area.
 4. An electronic-parts mounting board frame according to claim1, in which either the ends of said outer leads or the second ends ofsaid inner leads are apertured.
 5. An electronic-parts mounting boardframe according to claim 1, in which the ends of said outer leads andthe second ends of said inner leads are half-etched, and the half-etchedends of said outer leads and the half-etched ends of said inner leadsare laid on one another to thereby join them together.
 6. Anelectronic-parts mounting board comprising:an insulating substrate; aplurality of inner leads mounted on said insulting substrate such thatends of said plurality of inner leads protrude from said insulatingsubstrate; and wherein said ends of said plurality of inner leads areelectrically connected to ends of a plurality of outer leads which areintegral with an electronic-parts mounting board frame.